title: Purification and characterization of methyl-accepting chemotaxis protein methyltransferase I in Bacillus subtilis.
abstract: A methyltransferase that methylates one of the proteins involved in chemotactic adaptation to sensory stimuli in Bacillus subtilis was purified to homogeneity. The enzyme utilizes S-adenosylmethionine as donor for a methyl group that is transferred to a glutamate residue in a 69 000-mol.wt. membrane protein and also to a protein of 19 000 mol.wt. The molecular weights of the denatured enzyme by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and of the native enzyme by gel-filtration chromatography both show the protein to be a 44 000-mol.wt. monomer. Isoelectric focusing of the purified methyltransferase showed the protein to be a single species with isoelectric point pI 5.4. On the basis of a molecular weight of 44 000, the molar absorption coefficient at 262 nm of the enzyme is 10.9 x 10(4) M-1 . cm-1. The Km of the enzyme for S-adenosylmethionine is about 2 microM. The Ki for S-adenosylhomocysteine is about 0.2 microM. Ca2+ is a competitive inhibitor of methylation, with a Ki of 0.065 microM. The enzyme methylates membranes from the wild-type more efficiently than membranes isolated from a mutant strain defective in chemotaxis. The enzyme is unable to methylate Escherichia coli membranes.
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology*; D002633:Chemotaxis; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D007700:Kinetics; D008745:Methylation; D008970:Molecular Weight; D011496:Protein Methyltransferases / Q000302:isolation & purification*; D011484:Protein-Arginine N-Methyltransferases / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D011496:Protein Methyltransferases; D011484:Protein-Arginine N-Methyltransferases